According to some prior art engine intake systems, the intake lines which lead to the inlet openings and the exhaust-gas lines which adjoin the outlet openings are at least partially integrated in the cylinder head, and are generally merged in each case so as to form at least one manifold.
In the case of the internal combustion engine to which the present description relates, the intake lines are merged to form an overall intake line, thus forming an intake manifold.
In general, the exhaust-gas lines of the cylinders are merged within the cylinder head so as to form an integrated exhaust manifold, that is to say the exhaust manifold is integrated e.g., entirely integrated) in the cylinder head. A cylinder head of said type is also characterized by a very compact design, which permits dense packaging of the drive unit as a whole. Furthermore, said exhaust manifold can benefit from a liquid-type cooling arrangement that may be provided in the cylinder head, such that the manifold does not need to be manufactured from thermally highly loadable and thus expensive materials, if desired.
The use of a cylinder head with an integrated manifold also leads to a reduced number of components, and consequently to a reduction in costs, in particular assembly and procurement costs.
The cylinder head of a modern internal combustion engine is generally thermally more highly loaded and therefore also places increased demands on the cooling arrangement, in particular if the cylinder head is equipped with an integrated exhaust manifold and/or the internal combustion engine is a supercharged internal combustion engine.
If the internal combustion engine has a liquid cooling arrangement, at least one coolant jacket is formed in the cylinder head, which coolant jacket conducts the coolant through the cylinder head; this necessitates a relatively complex cylinder head structure.
The above statements make it clear that the cylinder head of an internal combustion engine is a thermally and mechanically highly loaded component. In this context, it may be taken into consideration that an increasing proportion of internal combustion engines are supercharged—by means of exhaust-gas turbocharger or mechanical charger. On account of the ever more dense packaging in the engine bay and the increasing integration of parts and components into the cylinder head, for example the integration of the exhaust manifold, the thermal loading of the internal combustion engine and of the cylinder head is increased in particular, such that increased demands are placed on the cooling system.
In the case of direct-injection internal combustion engines, it may also be desired for the injection device of each cylinder to be arranged in the cylinder head close to the combustion chamber. This poses problems in particular in the case of internal combustion engines with two valves per cylinder, in the case of which the inlet opening and the outlet opening should be designed to be as large as possible in order to realize a satisfactory charge exchange, that is to say in order to ensure both good charging of the cylinder and an effective discharge of the combustion gases.
According to the prior art, the constricted space conditions in the cylinder head have the effect that the injection nozzle is arranged eccentrically and so as to be inclined relative to the cylinder longitudinal axis. This arrangement of the injection nozzle impedes the most extensive and uniform possible distribution of the fuel in the combustion chamber. This may be highly detrimental to the mixture formation and homogenization of the fuel-air mixture.
Space efficiency component packaging is also desirable in some engines. However, space efficient component packaging may be at odds with certain efficient engine manufacturing procedures.
Against the background of that stated above, one example engine objective is to provide a direct-injection internal combustion engine which is distinguished by improved mixture formation and which provides a satisfactory power output. A compact engine arrangement may be another objective of the engines described herein.
The objectives may at least partially be achieved by means of a direct-injection internal combustion engine having a cylinder head comprising at least three cylinders in an in-line arrangement along a longitudinal axis of the cylinder head, in which internal combustion engine, each cylinder has an inlet opening for the supply of combustion air into the cylinder via an intake system, each inlet opening being adjoined by an intake line, and the intake lines of the cylinders merging to form an overall intake line, thus forming an intake manifold, each cylinder has an outlet opening for discharging the exhaust gases via an exhaust-gas discharge system, each outlet opening being adjoined by an exhaust-gas line, each inlet opening is equipped with an inlet valve, and each outlet opening is equipped with an outlet valve, each cylinder comprises a piston articulately connected to a crankshaft, which piston oscillates along a cylinder longitudinal axis as the crankshaft rotates about an axis of rotation, the cylinder longitudinal axis being perpendicular to the axis of rotation of the crankshaft, and each cylinder is equipped with an injection nozzle for the direct introduction of fuel into the cylinder, and which internal combustion engine is distinguished by the fact that the cylinder-specific injection nozzle is arranged centrally, without a spacing to the cylinder longitudinal axis, and is oriented along the cylinder longitudinal axis.
In one example, each cylinder of the internal combustion engine according to the description may be equipped with an injection nozzle which is arranged centrally, that is to say in the middle, in the cylinder, specifically without a spacing to the cylinder longitudinal axis. Furthermore, the injection nozzle is oriented along the cylinder longitudinal axis and thus in the direction of the piston crown. This arrangement of the injection nozzle ensures or permits an extensive and uniform distribution of the fuel in the combustion chamber, whereby the mixture formation in the cylinder is assisted, in particular the homogenization of the fuel-air mixture in the short time available.
The objective on which the engine is based is thus achieved, that is to say a direct-injection internal combustion engine is provided which is distinguished by improved mixture formation and which provides a satisfactory power output.
Further advantageous embodiments of the direct-injection internal combustion engine will be discussed in greater detail herein.
Embodiments of the direct-injection internal combustion engine may be advantageous in which the cylinder head comprises three or five cylinders in an in-line arrangement, the intake manifold being of asymmetrical design such that the overall intake line is arranged eccentrically with respect to the manifold.
In the present case, as an example, the cylinder head may have an intake manifold of asymmetrical design, in the case of which the overall intake line is arranged not in the center of the manifold but eccentrically. In this way, in the case of cylinder heads with three, four or five cylinders, the overall intake line can be arranged with an equal spacing to a front face side of the cylinder head. This offers advantages for example if a traction drive mechanism is provided on the front face side of the cylinder head and a generator that can be driven by said traction drive mechanism is to be arranged between the front face side and the overall intake line.
Regardless of the respective number of cylinders, it is then possible for a structurally identical generator to be used, which, in cylinder heads with different numbers of cylinders, is positioned and fastened at the same location and interlinked or connected with the rest of the structure surrounding the generator.
That which has been stated above applies for example to an engine family which comprises cylinder heads with three, four and five cylinders. In the case of cylinder heads with four cylinders, it would then be possible for the intake manifold to be of symmetrical form, such that the overall intake line is arranged centrally between the two inner cylinders, that is to say between the second and third cylinders. In the case of cylinder heads with three and five cylinders, the intake manifold would be of asymmetrical form, specifically such that the overall intake line is arranged eccentrically, but again between the second and third cylinders, wherein the cylinders are numbered consecutively starting from the front face side of the cylinder head; from one to three or from one to five.
The eccentric arrangement of the overall intake line, that is to say of the intake manifold of asymmetrical form according to the description, can also be utilized advantageously in conjunction with other parts of the internal combustion engine, in particular auxiliary assemblies, specifically whenever it is possible to benefit from the fact that the overall intake line is arranged in an unchanged manner between the second and third cylinders irrespective of the number of cylinders of the cylinder head. These may also include the high-pressure pump of a fuel direct-injection means and/or the compressor of an air-conditioning system, which can be installed in an unchanged manner irrespective of the number of cylinders as long as the generator is positioned at the same location. The compressor of a supercharging arrangement may likewise be mentioned in this context. In this way, common components can be used in an engine line to achieved reduced engine manufacturing costs if desired. Furthermore, the components in the engines in the line may also be space efficiently packaged due to the profile of the intake manifolds in the different engines in the engine family.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.
FIGS. 1-6 are shown approximately to scale. However, other relative dimensions may be used, in other embodiments.